var timeout;
var timer_timeout;
var setup = false;

function getElement(name)
{
	if(document.all)		// IE4
	{
		return document.all[name];
	}
	if(document.layers)		// NN4
	{
		return document.layers[name];
	}
	if(document.getElementById)	// NN6 or IE/Opera 6
	{
		return document.getElementById(name);
	}
	return false;
}

function preload()
{
	for (var i = 0; i <= 19; i++)
	{
		var a = new Image();
		a.src = "pic" + i + ".jpg";
	}
}

function timer()
{
	timer_timeout = window.setInterval("timer_setup()", 5000);
}

function timer_setup()
{
	if (!setup) do_setup();
	timeout = window.setInterval("swap_image()", 3000);
}

function do_setup()
{
	window.clearInterval(timer_timeout);
	var obj = getElement("image");
	obj.onmouseover = function() { swap_image() };
	setup = true;
}

function swap_image()
{
	var zzahl = Math.round(Math.random()*19);
	var obj = getElement('image');
	obj.src = "pic" + zzahl + ".jpg";
}